This invention pertains to devices particularly useful where vertical measurements are necessary such as in road building and similar construction where a paving string is required to be held at a certain vertical distance above surveyor's stakes or hubs, or in surveying where the surveyor's rod must be held vertically.
Before paving a road with a hard surfacing material either concrete or asphaltic cement, the level of that surface is accurately surveyed using carefully calibrated instruments. The level thus set is converted into measurements indicating the distance above ground level at various stations along the road. The surveyor then sets a stake called a hub at a fixed distance from the edge line of the paving and a nail or the like set at a given level. Above that level, a line called a string line is set. The line is at a fixed horizontal and vertical distance from the edge of the paving. Those distances are set by the machine which lays the pavement. This line is stretched tautly between those stations at proper level in order to determine what the level of the surface of the paving material should be.
The paving string line is connected between stakes to which the string has been fastened at the proper distance above the surface. However, in order to be as accurate as possible, the distance above the surface should be measured on a vertical line because the surveys are conducted based on vertical measurement. Currently, many road top milling machines, particularly those used for ground surface milling, and paving machines operate from such string lines. Usually a single line is necessary for the milling machine, although dual lines are usually used by paving machines. These lines are attached by longitudinal extensions to a stake set some distance from the edge of the new surface.
Currently, the determination of distance above the surface is determined by having one worker hold a measuring device in as close to a vertical position as possible while another positions the paving string. By using the present invention, a single worker can set this holding stand and plumb finder, and then by bending over or kneeling down while the plumb finder is held by the holder device that same worker can adjust the horizontal extension on its stake to fasten the string at the proper level, thus avoiding the need for a second worker and saving the contractor a substantial extra expense by reducing the time necessary for this function, and increasing the accuracy of the string level.
Similarly in the process of surveying, the surveyor's rod is normally held by one person while another uses the instrument. In order to achieve a vertical position, the rod holder, except in unusual circumstances, is required to rock the rod back and forth to acquire an accurate measurement. Use of the device of the current invention will assure accuracy without requiring assistance of a person to hold the rod, or, if the assistant is present, the process of rocking the rod is unnecessary.